Meningoencephalitis in a polar bear caused by equine herpesvirus 9 (EHV-9).
Authors: Donovan T A, Schrenzel M D, Tucker T, Pessier A P, Bicknese B, Busch M D M, Wise A G, Maes R, Kiupel M, McKnight C, Nordhausen R W
Journal: Veterinary pathology
Summary
# Editorial Summary A 12-year-old captive polar bear presented with acute neurological signs including tremors, seizures, and circling behaviour, progressing to generalised seizures despite inconclusive initial diagnostics. Post-mortem examination and immunohistochemistry revealed multifocal nonsuppurative meningoencephalitis with characteristic intranuclear inclusion bodies throughout the cerebral cortex, thalamus, and brainstem, with polymerase chain reaction confirming equine herpesvirus 9 (EHV-9) as the causative agent. This case represents the first documented fatal EHV-9 infection in a non-equine species and demonstrates the significant pathogenic potential of this virus when transmitted across species barriers, likely resulting from direct or indirect contact with infected equids. The severity of neurological disease and rapid progression to euthanasia highlights a critical infection control consideration for facilities housing both equids and other mammalian species, particularly given the zoo setting in which this animal was maintained. Equine professionals should recognise that herpesviruses—particularly EHV-9—pose zoonotic or cross-species risks that extend beyond equine populations, reinforcing the importance of rigorous biosecurity protocols and careful management of equids in mixed-species environments.
Read the full abstract on PubMed
Practical Takeaways
- •EHV-9 poses a zoonotic/cross-species transmission risk; strict biosecurity protocols essential when handling equids in mixed animal facilities or zoos
- •Fatal encephalitis can occur in non-equine species exposed to EHV-9, highlighting need for careful quarantine and hygiene when managing equids near other animals
- •Sudden onset neurological signs in animals with equid exposure history warrant consideration of herpesvirus as differential diagnosis
Key Findings
- •Equine herpesvirus 9 caused fatal meningoencephalitis in a polar bear with multifocal nonsuppurative inflammation of cerebral cortex, thalamus, midbrain, and medulla
- •PCR confirmed EHV-9 as the causative agent, demonstrating zoonotic/interspecies transmission capability
- •Clinical presentation included progressive neurological signs (tremors, seizures, circling, ptyalism) with nonspecific CSF pleocytosis